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      1 =pod
      2 
      3 =head1 NAME
      4 
      5 X509_LOOKUP_hash_dir, X509_LOOKUP_file, X509_LOOKUP_store,
      6 X509_load_cert_file_ex, X509_load_cert_file,
      7 X509_load_crl_file,
      8 X509_load_cert_crl_file_ex, X509_load_cert_crl_file
      9 - Default OpenSSL certificate lookup methods
     10 
     11 =head1 SYNOPSIS
     12 
     13  #include <openssl/x509_vfy.h>
     14 
     15  X509_LOOKUP_METHOD *X509_LOOKUP_hash_dir(void);
     16  X509_LOOKUP_METHOD *X509_LOOKUP_file(void);
     17  X509_LOOKUP_METHOD *X509_LOOKUP_store(void);
     18 
     19  int X509_load_cert_file_ex(X509_LOOKUP *ctx, const char *file, int type,
     20                             OSSL_LIB_CTX *libctx, const char *propq);
     21  int X509_load_cert_file(X509_LOOKUP *ctx, const char *file, int type);
     22  int X509_load_crl_file(X509_LOOKUP *ctx, const char *file, int type);
     23  int X509_load_cert_crl_file_ex(X509_LOOKUP *ctx, const char *file, int type,
     24                                 OSSL_LIB_CTX *libctx, const char *propq);
     25  int X509_load_cert_crl_file(X509_LOOKUP *ctx, const char *file, int type);
     26 
     27 =head1 DESCRIPTION
     28 
     29 B<X509_LOOKUP_hash_dir> and B<X509_LOOKUP_file> are two certificate
     30 lookup methods to use with B<X509_STORE>, provided by OpenSSL library.
     31 
     32 Users of the library typically do not need to create instances of these
     33 methods manually, they would be created automatically by
     34 L<X509_STORE_load_locations(3)> or
     35 L<SSL_CTX_load_verify_locations(3)>
     36 functions.
     37 
     38 Internally loading of certificates and CRLs is implemented via functions
     39 B<X509_load_cert_crl_file>, B<X509_load_cert_file> and
     40 B<X509_load_crl_file>. These functions support parameter I<type>, which
     41 can be one of constants B<FILETYPE_PEM>, B<FILETYPE_ASN1> and
     42 B<FILETYPE_DEFAULT>. They load certificates and/or CRLs from specified
     43 file into memory cache of B<X509_STORE> objects which given B<ctx>
     44 parameter is associated with.
     45 
     46 Functions B<X509_load_cert_file> and
     47 B<X509_load_crl_file> can load both PEM and DER formats depending of
     48 type value. Because DER format cannot contain more than one certificate
     49 or CRL object (while PEM can contain several concatenated PEM objects)
     50 B<X509_load_cert_crl_file> with B<FILETYPE_ASN1> is equivalent to
     51 B<X509_load_cert_file>.
     52 
     53 Constant B<FILETYPE_DEFAULT> with NULL filename causes these functions
     54 to load default certificate store file (see
     55 L<X509_STORE_set_default_paths(3)>.
     56 
     57 
     58 Functions return number of objects loaded from file or 0 in case of
     59 error.
     60 
     61 Both methods support adding several certificate locations into one
     62 B<X509_STORE>.
     63 
     64 This page documents certificate store formats used by these methods and
     65 caching policy.
     66 
     67 =head2 File Method
     68 
     69 The B<X509_LOOKUP_file> method loads all the certificates or CRLs
     70 present in a file into memory at the time the file is added as a
     71 lookup source.
     72 
     73 File format is ASCII text which contains concatenated PEM certificates
     74 and CRLs.
     75 
     76 This method should be used by applications which work with a small
     77 set of CAs.
     78 
     79 =head2 Hashed Directory Method
     80 
     81 B<X509_LOOKUP_hash_dir> is a more advanced method, which loads
     82 certificates and CRLs on demand, and caches them in memory once
     83 they are loaded. As of OpenSSL 1.0.0, it also checks for newer CRLs
     84 upon each lookup, so that newer CRLs are as soon as they appear in
     85 the directory.
     86 
     87 The directory should contain one certificate or CRL per file in PEM format,
     88 with a filename of the form I<hash>.I<N> for a certificate, or
     89 I<hash>.B<r>I<N> for a CRL.
     90 The I<hash> is the value returned by the L<X509_NAME_hash_ex(3)> function
     91 applied to the subject name for certificates or issuer name for CRLs.
     92 The hash can also be obtained via the B<-hash> option of the
     93 L<openssl-x509(1)> or L<openssl-crl(1)> commands.
     94 
     95 The .I<N> or .B<r>I<N> suffix is a sequence number that starts at zero, and is
     96 incremented consecutively for each certificate or CRL with the same I<hash>
     97 value.
     98 Gaps in the sequence numbers are not supported, it is assumed that there are no
     99 more objects with the same hash beyond the first missing number in the
    100 sequence.
    101 
    102 Sequence numbers make it possible for the directory to contain multiple
    103 certificates with same subject name hash value.
    104 For example, it is possible to have in the store several certificates with same
    105 subject or several CRLs with same issuer (and, for example, different validity
    106 period).
    107 
    108 When checking for new CRLs once one CRL for given hash value is
    109 loaded, hash_dir lookup method checks only for certificates with
    110 sequence number greater than that of the already cached CRL.
    111 
    112 Note that the hash algorithm used for subject name hashing changed in OpenSSL
    113 1.0.0, and all certificate stores have to be rehashed when moving from OpenSSL
    114 0.9.8 to 1.0.0.
    115 
    116 OpenSSL includes a L<openssl-rehash(1)> utility which creates symlinks with
    117 hashed names for all files with F<.pem> suffix in a given directory.
    118 
    119 =head2 OSSL_STORE Method
    120 
    121 B<X509_LOOKUP_store> is a method that allows access to any store of
    122 certificates and CRLs through any loader supported by
    123 L<ossl_store(7)>.
    124 It works with the help of URIs, which can be direct references to
    125 certificates or CRLs, but can also be references to catalogues of such
    126 objects (that behave like directories).
    127 
    128 This method overlaps the L</File Method> and L</Hashed Directory Method>
    129 because of the 'file:' scheme loader.
    130 It does no caching of its own, but can use a caching L<ossl_store(7)>
    131 loader, and therefore depends on the loader's capability.
    132 
    133 =head1 RETURN VALUES
    134 
    135 X509_LOOKUP_hash_dir(), X509_LOOKUP_file() and X509_LOOKUP_store()
    136 always return a valid B<X509_LOOKUP_METHOD> structure.
    137 
    138 X509_load_cert_file(), X509_load_crl_file() and X509_load_cert_crl_file() return
    139 the number of loaded objects or 0 on error.
    140 
    141 =head1 SEE ALSO
    142 
    143 L<PEM_read_PrivateKey(3)>,
    144 L<X509_STORE_load_locations(3)>,
    145 L<SSL_CTX_load_verify_locations(3)>,
    146 L<X509_LOOKUP_meth_new(3)>,
    147 L<ossl_store(7)>
    148 
    149 =head1 HISTORY
    150 
    151 The functions X509_load_cert_file_ex(),
    152 X509_load_cert_crl_file_ex() and X509_LOOKUP_store() were added in
    153 OpenSSL 3.0.
    154 
    155 =head1 COPYRIGHT
    156 
    157 Copyright 2015-2021 The OpenSSL Project Authors. All Rights Reserved.
    158 
    159 Licensed under the Apache License 2.0 (the "License").  You may not use
    160 this file except in compliance with the License.  You can obtain a copy
    161 in the file LICENSE in the source distribution or at
    162 L<https://www.openssl.org/source/license.html>.
    163 
    164 =cut
    165